1. Field of the Invention
The present invention relates to a developer cartridge for exchanging developers in a developing apparatus which develops an electrostatic latent image, and an image forming apparatus using this developer cartridge.
2. Description of the Related Art
In an image forming apparatus such as a copying machine, a printer or a facsimile etc, an electrostatic latent image is formed on a latent image carrier like a photosensitive drum. A developing apparatus is used to develop an electrostatic latent image with a developer. A typical developer used in the developing apparatus is composed of two components, toner and carrier. As the toner in this developer is consumed in a developing process, the toner should be supplemented. Further, the developer in the developing apparatus is deteriorated with the passage of time so that the quality of an image becomes lower. It is therefore necessary to exchange the old developer with a new one. Recently, this exchange is often conducted by the user of the image forming apparatus. In this respect, there is a demand for an image forming apparatus designed to facilitate the developer exchange without making the operator's hands dirty.
In general, the developer exchange is conducted as follows. A developer cartridge containing an unused developer and an empty collecting cartridge for collecting the developer in the developing apparatus are placed in the developing apparatus. Then, after the developer in the developing apparatus is collected in the collecting cartridge, the unused developer is supplied into the developing apparatus from the developer cartridge. This method involves two cartridges, thus complicating the exchange.
For example, U.S. Pat. No. 5,109,254 proposed a developer cartridge having those two cartridges designed as a single cartridge to ensure automatic exchange of developers. In the proposed method, a developer exchanging section is provided on a side of the developing apparatus. The developer cartridge comprises a cylindrical portion, a developer storage room which is located above the cylindrical portion and where an used developer is retained, and a collecting room located under the cylindrical portion. This developer cartridge is placed in the developer exchanging section of the developing apparatus. More specifically, the cylindrical portion of the developer cartridge is fitted in the developer exchanging section of the developing apparatus.
When the shutter of the collecting room of the developer cartridge is open, the used developer in the developing apparatus falls into the collecting room from the developer exchanging section. Then, the shutter of the collecting room is closed and the shutter of the developer storage room is open. As a result, the unused developer in the developer storage room falls into the developer exchanging section to be supplied into the developing apparatus. The developer in the developing apparatus is exchanged with an used developer in this manner.
This method is effective when there is a small amount of the developer to be exchanged. When there is a large amount of the developer to be exchanged, however, it is necessary to make the developer storage room and collecting room of the developer cartridge longer. In this case, the developer cartridge inevitably becomes larger in length. This makes the handling of the developer cartridge troublesome, and requires extra space for storage of such developer cartridges. It is also necessary to provide extra space for placing the developer cartridge in the developing apparatus. In addition, as the developer exchanging section of the developing apparatus is used only for developer exchange, it is cost effective to make this section smaller. But, it is troublesome to conduct the developer exchange in the small exchanging space.